Printed antennas are well known. Conventional printed antennas are manufactured by printing an antenna structure on a carrier using a conductive ink, for example a silver ink. It is known that silver ink starts to oxidize and discolor when exposed to air. Such an oxidation is known to deteriorate the electrical performance of the antenna structure printed with the silver ink. In order to prevent oxidation, it is known to cover the printed antenna structure with a protection layer made of varnish. The varnish layer, however, is also known to deteriorate the electrical performance of the printed antenna. The antenna efficiency of a printed antenna covered with a varnish layer is lower than the antenna efficiency of a printed antenna without a covering varnish layer.
It is further known that conventional printed antennas having an antenna structure printed with a conductive ink possess poor mechanical properties that make it difficult to electrically connect the antenna.
FIG. 14 shows a sectional view of a conventional antenna 20 having a foil sheet 21 with a front side 26 and an opposed back side 27. A printed antenna structure 24 is arranged on the front side 26 of the foil sheet 21. An adhesive strip 22 is arranged on the back side 27 of the foil sheet 21. The adhesive strip 22 is glued to a carrier 23. The printed antenna structure 24 made of conductive ink is not protected by any covering layer.
A saddle shaped connector 25 is arranged between the printed antenna structure 24 and a contact pad arranged on a printed circuit board (PCB) 28. The connector 25 touches the printed antenna structure 24 in a contact point 29. The carrier 23 is pressed towards the connector 25 and the printed circuit board 28 to provide an electrical connection between the printed antenna structure 24 and the printed circuit board 28.
When the antenna 20 of FIG. 14 undergoes a rapid change of temperature, for example a change from −40° C. to +85° C., different coefficients of thermal expansion of the various materials used for the antenna 20 cause the contact point 29 to laterally move over the surface of the printed antenna structure 24. This, combined with the force used to press the carrier 23 towards the connector 25 and the printed circuit board 28 and the specific contact interface shape (radius) of the connector 25 causes damage to the ink layer of the printed antenna structure 24. The conductive ink of the printed antenna structure 24 eventually gets pushed aside, resulting in a poor electrical connection between the connector 25 and the printed antenna structure 24.